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Detection of Chamber Conditioning by CF4 in the GEC CellDuring oxide etch processes, buildup of fluorocarbon residues on reactor sidewalks can cause to drift and will necessitate time for conditioning and cleaning of the reactor. Various measurements in CF4 and Ar plasmas are made in an attempt to identify a metric able to indicate the chamber condition. Mass spectrometry and a Langmuir probe shows that the buildup of fluorocarbon films on the reactor surface causes a decrease in plasma floating potential, plasma potential, and ion energy in argon plasmas. This change in floating potential is also observed in CF4 plasma operation, and occurs primarily during the first hour and a half of plasma operation. A slight rise in electron density is also observed in the argon plasmas. Because the change is seen in an argon plasma, it is indicative of altered physical, not chemical, plasma-surface interactions. Specifically, the insulating films deposited on metal surfaces alter the electromagnetic fields seen by the plasma, affecting various parameters including the floating potential and electron density. An impedance probe placed on the inductive coil shows a slight reduction in plasma impedance due to this rising electron density. The optical emission of several species, including CF, C2, atomic Si and atomic C, is also monitored for changes in density resulting from the buildup of film on the chamber wall. Changes in the optical emission spectrum are comparable to the noise levels in their measurement.
Document ID
20020039747
Acquisition Source
Ames Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Cruden, Brett A.
(NASA Ames Research Center Moffett Field, CA United States)
Rao, M. V. V. S.
(NASA Ames Research Center Moffett Field, CA United States)
Sharma, S. P.
(NASA Ames Research Center Moffett Field, CA United States)
Meyyappan, M.
(NASA Ames Research Center Moffett Field, CA United States)
Arnold, James
Date Acquired
August 20, 2013
Publication Date
January 1, 2001
Subject Category
Inorganic, Organic And Physical Chemistry
Funding Number(s)
PROJECT: RTOP 632-62-01
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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